An alert viewer complains to us, regarding some of the ample evidence we’ve presented that more CO2 helps plants of all kinds grow, that “my alarmist sister finally accepted CO2 makes stuff grow better – so then her argument was that it was of a lower quality.” Which recalls a long-ago (March 13,1987, in fact) complaint in National Review that “CBS reports that though the unemployment rate is down, many people aren’t happy with the jobs they’re getting…. Next we expect CBS to report that though nobody’s starving, the food tastes lousy.” Or, as Earth.com just put it “Rising carbon dioxide makes crops grow bigger but less nutritious”. Rats. If only farmers could adjust nutrient levels in crops through fertilizer application.

Alarmists being creative and independent thinkers are now declaring CO₂ aka plant food to be the latest big threat to plants. Including SciTechDaily with “Increasing Levels of CO2 Results in Less Nutritious Crops”. Or Hopkins Bloomberg Public Health, for instance:

“Less Nutritious Crops: Another Result of Rising CO2/ Rising carbon levels are eroding nutritional values of staple crops, threatening millions with hidden hunger.”

Hidden hunger? What’s that, the kind where you feel full but are secretly empty?

Well, no. Surely if they’re qualified to write on it they’ve heard of “Liebig’s Law of the Minimum” which states that what determines plant growth is not the total availability of desirable things but the scarcest resource. Which means that you could have more CO2 and less healthy, nutritious or indeed flavourful plants if there was a critical shortage of something else. For instance water.

Or, in that HBPH “Planetary Health” piece, some farmer in Mississippi whose salad greens are more like browns because of “potassium deficits”. Which has what exactly to do with CO2? Well, you know how alarmism works. See, farmer Timothy Robb:

“can sprinkle chicken manure and study soil composition in the hopes of righting the ratios. But there’s another disrupting force he and other farmers can’t control: rising atmospheric carbon levels. Scientists investigating the impact of increasing carbon dioxide on global staple foods like rice and wheat have made some concerning findings: Higher CO2 levels make many foods less nutritious, reducing protein, vitamins, and critical micronutrients like zinc and iron. Micronutrient deficiency, or ‘hidden hunger,’ is already a pervasive problem globally as a result of poor and restricted diets. A lack of crucial vitamins and minerals can affect humans in a number of ways, from increasing child and maternal mortality to impairing growth and development. More than 2 billion people worldwide currently face micronutrient deficiencies, including more than half of preschool children and about two-thirds of non-pregnant women of reproductive age, research has estimated.”

No doubt they do. Lack of fertilizer, impoverished soil, a variety of things that have haunted humanity since the invention of farming are still problems in the poorer nations. But the evidence that it’s getting worse? And what’s the mechanism with CO2? According to the piece, drawing heavily on “Samuel Myers, principal research scientist in environmental health at Harvard University”, it argues that:

“Crops grown under higher-carbon conditions increase the synthesis of sugars and starches while decreasing the concentrations of protein and nutrients. These findings are evident in global staple foods including rice, wheat, potatoes, and barley. (A much smaller percentage of plants like corn and sugarcane use carbon differently and haven’t demonstrated the same changes.)”

Now to get all nit-picky, corn and sugarcane are, yes, our new friends the C4 plants, specifically adapted to… what’s this? Lower CO2 levels? Correct. Whereas those that evolved when CO2 levels were far higher than they are today are wilting because CO2 levels are rising a bit? Pfui.

The piece says:

“The precise mechanisms fueling the decline are still a mystery but likely have roots in the imbalance created by additional CO2, which the plant takes from the air and uses in photosynthesis. As plants pull water from the soil, they bring along nutrients like iron and manganese which help the plant grow. Adding more CO2 shifts the proportions, much like adding more of just one ingredient to a recipe.”

So the fact that more CO2 allows plants to make do with less water, a crucial factor in global greening as they survive and even flourish in drier areas including at higher altitudes, is now presented as bad for them? Or is the crucial mechanism research funding that seeks to prove that CO2 is bad bad bad?

A paper in Science Daily in 2022 agrees that plants don’t know what’s good for them. The press release says:

“While increased carbon dioxide levels in the atmosphere encourage plant growth, they also reduce the nutritional value of plants, which can have a larger impact on nutrition and food safety worldwide. Researchers have discovered a new way plants are adapting to the changing climate – information that can be used to help plants grow strong while also maintaining their nutritional value.”

But again someone’s a monster ignoramus here. Plants have been adapting for tens of millions of years to “the changing climate” in which temperature and CO2 declined, including as noted the appearance of C4 photosynthesis. As for the actual study, it suggested that with more CO2 plants take up less phosphorus. Maybe because they need it less? Maybe CO2 not phosphorus was the Liebig minimum factor?

No no no. It’s carbon pollution. And indeed according to the researchers, when they tried to “force the plant to put a lot of phosphorus in the chloroplast, the plaint failed to grow”. Almost as if it knew what it was doing and you didn’t.

The New York Times was on the climate-change-ate-my-veggies thing early. In 2018 it said:

“How More Carbon Dioxide Can Make Food Less Nutritious/ Carbon dioxide helps plants grow. But a new study shows that rice grown in higher levels of carbon dioxide has lower amounts of several important nutrients.”

They cited a study that rice with more CO2 had less protein, iron, zinc and various B vitamins but more E. It’s a bit hard to understand how plants could be so maladapted especially if evolution is so wonderful. But we suspect that researchers have begun to realize that the global greening argument is a strong one against the orthodox position and they’d better find some way of making green the new brown. And again, “diluting” minerals might be another way of saying a healthier plant needs fewer of them not that it’s so healthy it’s sick. And where’s the evidence, which surely would be important and ought to be readily available, that the greater growth of plants including food crops in the last four decades has actually increased malnutrition? Or is the inconvenient truth that just as extreme poverty has declined sharply, so has the ancient curse of hunger in all its forms?

Scientific American also rushed into the breach early, with a piece “Ask the Experts: Does Rising CO2 Benefit Plants?” whose subhed tried to stop it before it started: “Climate change’s negative effects on plants will likely outweigh any gains from elevated atmospheric carbon dioxide levels”. QED. But after a shot at “[c]limate change skeptics” and their devious arguments, the piece did admit there was something to discuss:

“So is it true rising atmospheric CO2 will help plants, including food crops? Scientific American asked several experts to talk about the science behind this question. There is a kernel of truth in this argument, experts say, based on what scientists call the CO2 fertilization effect.”

Oh, that thing where it’s crucial plant food? Why yes:

“’CO2 is essential for photosynthesis,’ says Richard Norby, a corporate research fellow in the Environmental Sciences Division and Climate Change Science Institute of Oak Ridge National Laboratory.”

And your high school biology teacher. But fear not that you must fear not:

“Norby notes the results scientists produce in labs are generally not what happens in the vastly more complex world outside; many other factors are involved in plant growth in untended forests, fields and other ecosystems. For example, ‘nitrogen is often in short enough supply that it’s the primary controller of how much biomass is produced’ in an ecosystem, he says. ‘If nitrogen is limited, the benefit of the CO2 increase is limited…. You can’t just look at CO2, because the overall context really matters.’”

Which is about like saying that hunger isn’t a big problem because even someone who’s not starving can drown. But then there’s the zinc… and the same expert who says:

“Rising CO2’s effect on crops could also harm human health. ‘We know unequivocally that when you grow food at elevated CO2 levels in fields, it becomes less nutritious,’ notes Samuel Myers, principal research scientist in environmental health at Harvard University. ‘[Food crops] lose significant amounts of iron and zinc – and grains [also] lose protein.’”

Yup. Same Samuel Myers. When in doubt…

In 2024 MIT’s Climate Portal conducted what seems an especially flimsy last-ditch defence of CO2 being bad for plants despite being good for them:

“It’s true that plants love CO2. During photosynthesis, they take in carbon dioxide and, with the assistance of water and sunlight, make energy for themselves while releasing oxygen for us to breathe. Plants have been around for billions of years and have lived on Earth at times when the planet had far more CO2 in the air than it does now. So, would plants prefer a more carbon-heavy planet, like the one humans are now creating with our greenhouse gas emissions? Not necessarily, says David Des Marais, an MIT Professor of Civil and Environmental Engineering who studies how plants respond to their environments. ‘The short answer,’ Des Marais says, ‘is that most plants will grow faster and bigger with extra atmospheric CO2—all else being equal.’ However, plant growth is too complex for a one-size-fits-all law like ‘more CO2 is better.’ Experiments in which scientists piped extra CO2 into plant-growing chambers have proven this basic science: the additional carbon makes plants grow faster if you maintain other factors, such as soil nutrient and water availability. Yet things may not be so simple for the planet at large, Des Marais says.”

And then he actually made what is, in this context, a reasonable argument. Instead of saying yeah, sure, you’d get big healthy sickly little plants, he warned that CO2 isn’t the only factor so if climate change causes drought then plants short of water may shrivel. If, though the historical and prehistoric record does not support any such idea.

So instead the piece winds up saying you’ll die into the salad or something:

“Des Marais says some people point to climates of deep history as proof that plants can endure or even enjoy very high concentrations of carbon in the air. We know from the geologic record that hundreds of millions of years ago, Earth had an atmospheric CO2 level in excess of 2,000 parts per million (ppm). That’s compared to around 280 ppm in pre-industrial times and 417 ppm in 2022. Although plenty of plants lived through that period – albeit different species and in different places than today – humans did not. Such a CO2 level would produce year-round scorching temperatures akin to what we experience in summer today. In other words, he says, ‘this is not a period we would ever want to visit.’”

Leaving aside the weird confusion about pre-industrial times versus… um… pre-pre-industrial times maybe, the idea that the Jurassic was “scorching” rather than lush is just wrong.